Conventional rack-type straighteners for use in automotive collision repair and having working beams at or near 90 degrees to the perimeter beams are generally acceptable for use in repairing older cars with heavy, thick frames. The vectoring of these 90 degree beams has been relatively simple for purposes of achieving a diagonal repair since the corrective forces are centered separately from one another and do not tend to create distortion or damage on these older vehicles; however, in accordance with up-dated construction techniques, the newer unibody cars are built in a much lighter manner with 14, 16 and 18 gauge steel rails and the use of this conventional rack-type straightener when hooked up to these newer unibody cars may well in fact result in more damage rather than repairing the already present damage.
The newer small car designs also present interference problems with respect to the location of the work beams due to the closeness of the chassis beams on the vehicle.
There are conventional straighteners in which work beams can be diagonally positioned across the straightener and locked in that diagonal positon for use in repairing damage requiring diagonal pressure closer to the outer boundary of the vehicle. With these arrangements, a tower and pull-jack is installed to pull the damage outwardly, however, to extend this diagonal pull beneath the chassis area requires difficult hook-ups which, in many instances, are prone to accidents because the tower arm axis is never in line with the direction of the pull so that the tower has a tendency to lean. In order to counter this lean the perimeter bed must be additionally reinforced making the bed extremely thick and wide, further hampering access to the vehicle.
One example of a straightener, as described immediately above, is shown in U.S. Pat. No. 4,281,532, issued Aug. 4, 1981 to Covington. Here it will be seen that the cross beams can be moved to different angled positions and once in position must be locked, relative to the main support frame. A tower, as described above, is then used to provide diagonal pressure across the beams for effecting certain repair jobs.
As will be appreciated from the Covington patent, many different locking positions for the work beams must be provided to assure the beam can be moved to an accurate position. Furthermore, the Covington structure is extremely congested with parts such as the locking pins being relatively inaccessible, making it awkward to change positions for any of the transverse beams. The straightener of this patent is relatively inflexible and difficult for use in different types of hook-ups. A further drawback of the Covington structure lies in the hydraulic jacks that must be used to control reciprocal movement of the work beams with each of these hydraulic jacks being permanently located in position. Therefore, a hydraulic jack must be provided for each position to which the work beam is to be moved, otherwise the work beam cannot be moved under force of the piston across the frame of the straightener device.